DT McDonald will have MRI on biceps injury Monday

Three weeks after losing starting nose tackle Ian Williams for the season with a broken ankle, the 49ers are hoping another member of their defensive front didn’t sustain a similarly serious injury Sunday.

Defensive tackle Ray McDonald left in the third quarter with an injury to his right biceps. McDonald was injured when he was fighting off a block on his way to a tap-down sack of Texans quarterback Matt Schaub in San Francisco’s 34-3 win.

McDonald will have an MRI on Monday to determine the extent of the injury.

McDonald acknowledged he was concerned: “Yeah. I am. They said it’s not that bad, so I’ll see tomorrow.”

McDonald was replaced by Tony Jerod-Eddie, 23, a former undrafted free agent who had an interception in the fourth quarter. If McDonald’s injury is serious, the 49ers could re-explore the possibility of signing former All-Pro defensive lineman Richard Seymour. The team reached out to Seymour after the linebacker Aldon Smith entered a treatment facility, but the two sides couldn’t agree on financial terms, CBS Sports reported Sunday.

Jerod-Eddie said he was hopeful McDonald’s injury wasn’t severe, but was prepared for an increased workload. Jerod-Eddie became the first 49ers defensive lineman to record an interception since McDonald returned a pick 31 yards for a touchdown on Oct. 24, 2010.

Said Jerod-Eddie: “If I have to play a little more, I’ll be more than ready to do that.”

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In his second career start, inside linebacker Michael Wilhoite, 27, had 11 tackles, including three for losses, and defended a pass. Wilhoite also had two special-teams tackles as he filled for sidelined All-Pro Patrick Willis (groin) for a second straight week.

“It just says that says we have guys two and three deep at so many positions that can come in and won’t hurt the team,” Wilhoite said. “Guys can get hurt and we won’t feel like we have nothing left.”

Willis was on the field about two hours before kickoff and tested his injury under the supervision of director of sports medicine Jeff Ferguson and strength and conditioning coach Mark Uyeyama. Willis moved well when doing simulated backdrops, but never ran at full speed.

“He was really trying to (play), really eager to,” Jim Harbaugh said. “We just made the decision, really right before game time, that it was best (for him) not to play. Didn’t want to do anything stupid.”